Molecular subtractive surface-energy engineering of crosslinked Poly(4-vinylphenol) insulators for a solution-processed organic thin-film transistor

We propose a feasible method of manipulating the surface energy of crosslinked poly(4-vinylphenol) (c-PVP) thin films through the surface compositional modification assisted by an etchant. A physical picture of the surface-energy manipulation of c-PVP thin films based on the surface-selective molecular subtractive approach is clarified by investigating the chemical composition of the c-PVP film surfaces. We reveal that the molecular detachment by solvation on the surface leads to a reduction in the surface PVP density, thereby decreasing residual hydroxyl groups on the surface. In particular, it is found that the surface energy of a c-PVP thin film can be controlled by exploiting the thermal-treatment-time dependence of the soluble-PVP density. Organic thin-film transistors (TFTs) are fabricated via a solution process for demonstrating the applicability of our surface-energy-engineered c-PVP film as a gate insulator. The TFTs with the engineered c-PVP gate insulators exhibit improved electrical characteristics, compared to those with ordinary c-PVP gate insulators.